44 basic knowledge points about motors
1. The current of the single-phase transformer at no load is out of phase with the main magnetic flux, and there is a phase angle difference aFe because of the iron consumption current. The no-load current is a sharp top waveform because of the large third harmonic.
2. AC current flows in the armature windings of DC motors. However, DC current flows in the field winding. The excitation methods of DC motors include separate excitation, parallel excitation, series excitation, compound excitation and so on.
3. The back-EMF expression of the DC motor is E=CEFn; and the electromagnetic torque expression is Tem=CTFI.
4. The number of parallel branches of the DC motor is always in pairs. The number of parallel branches of the AC winding is not necessarily.
5. In a DC motor, the components of a single-stack winding are connected in series in a way that one is stacked on top of the other. Whether it is a single-wave winding or a single-stack winding, the commutator piece connects all the elements in series to form a single closed loop.
6. Asynchronous motor is also called induction motor, because the rotor current of asynchronous motor is generated by electromagnetic induction.
7. When the asynchronous motor is started under reduced voltage, the starting torque decreases, and the starting torque decreases in proportion to the square of the starting current of the winding.
8. When the amplitude and frequency of the primary side voltage are unchanged, the saturation degree of the transformer core is basically the same, and the excitation reactance is also basically the same.
9. The short-circuit characteristic of the synchronous generator is a straight line, and the magnetic circuit is unsaturated when the three-phase symmetrical short-circuit occurs; when the three-phase symmetrical steady-state short-circuit, the short-circuit circuit is a purely demagnetized direct axis component.
10. The current in the excitation winding of the synchronous motor is a direct current, and the excitation methods mainly include excitation generator excitation, static rectifier excitation, and rotary rectifier excitation.
11. There are no even harmonics in the three-phase composite magnetomotive force; symmetrical three-phase currents flow through the symmetrical three-phase windings, and the composite magnetomotive force does not have a multiple of 3 magnetic harmonics.
12. Three-phase transformers generally hope to have a delta connection on one side or grounding at the midpoint of one side. Because the winding connections of the three-phase transformer all hope to have the path of the third harmonic current.
13. When the symmetrical three-phase winding passes symmetrical three-phase current, the 5th harmonic in the synthesized magnetomotive force is reversed; the 7th harmonic is forward.
14. The mechanical characteristics of series-excited DC motors are relatively soft. The mechanical characteristics of separately excited DC motors are relatively hard.
15. The transformer short-circuit test can measure the leakage impedance of the transformer winding; while the no-load test can measure the excitation impedance parameters of the winding.
16. The transformation ratio of the transformer is equal to the turns ratio of the primary winding to the secondary winding. The transformation ratio of a single-phase transformer can also be expressed as the ratio of the rated voltage on the primary and secondary sides.
17. Under normal excitation, the power factor of the synchronous generator is equal to 1; keep the output active power unchanged, and make the excitation current smaller than the normal excitation (underexcitation), the nature of the direct-axis armature response is to assist magnetization; keep the output active power When the excitation current is greater than the normal excitation (overexcitation), the nature of the direct-axis armature response is demagnetization.
18. In a DC motor, iron loss mainly exists in the rotor core (armature core), because the magnetic field of the stator core is basically unchanged.
19. In a DC motor, the first pitch y1 is equal to the number of slots between the first side and the second side of the component. The composite pitch y is equal to the number of slots between the upper element sides of the two elements connected in series.
20. In a DC motor, when saturation is not considered, the characteristic of the quadrature-axis armature response is to shift the position where the magnetic field is zero, but the magnetic flux per pole does not change. When the brush is located on the geometric neutral line, the armature reaction is of cross-magnetic nature.
21. In a DC motor, the component that converts external DC power into internal AC power is a commutator. The function of the commutator is to convert DC to AC (or vice versa).
22. In a synchronous motor, when the excitation flux F0 of the stator windings is the maximum value, the back-EMF E0 reaches the minimum value. When F0 reaches zero, E0 reaches the maximum value. The phase between F0 and E0 The relationship is F0 ahead of E090o. And the relational expression between E0 and F0 is: E0= 4.44f N kN1F0.
23. In the motor, the leakage flux refers to only the magnetic flux of the interlinked winding itself, and the back electromotive force generated by it can often be equivalent to a leakage reactance voltage drop (or negative reactance voltage drop).
24. There are two types of rotors for asynchronous motors:-squirrel cage type and winding type.
25. The slip rate s of an asynchronous motor is defined as the ratio of the difference between the synchronous speed and the rotor speed to the synchronous speed. When the asynchronous motor works in the motor state, the range of its slip rate s is 1>s>0.
26. The relationship between electromagnetic torque Tem and slip rate s of asynchronous motor Tem-s curve has three key points, namely the starting point (s = 1), the maximum electromagnetic torque point (s=sm), the synchronization point (s =0). When the rotor resistance of an asynchronous motor changes, the characteristics of the maximum electromagnetic torque Tem and the slip rate sm are: the size does not change, but the s position changes.
27. Asynchronous motors must absorb hysteresis reactive power from the grid for excitation.
28. A coil group is energized with alternating current, and its magnetomotive force changes over time with a pulsating nature. A single coil is energized with alternating current, and its magnetomotive force also has a pulsating property over time.
29. When a synchronous generator is connected to the grid, its three-phase terminal voltage is required to be the same as the three-phase voltage of the grid: frequency, amplitude, waveform, phase sequence (and phase), etc.
30. The rotor of a synchronous motor has two types: hidden pole and salient pole.
31. The equivalent number of phases of the squirrel cage rotor is equal to the number of slots, and the equivalent number of turns per phase is 1/2.
32. Three-phase symmetrical alternating current winding, through symmetrical three-phase alternating current, its fundamental composite magnetomotive force is a circular rotating magnetomotive force, the direction of rotation is from the axis of the leading phase winding to the axis of the lagging phase, and then down An axis of the lag phase.
33. There are two connection methods between the three-phase windings of the three-phase transformer: star and delta; the magnetic circuit has two structures: group type and core type.
34. The 6 odd-numbered connection group numbers of the three-phase transformer are 1, 3, 5, 7, 9, 11. The 6 even-numbered connection group numbers are 0, 2, 4, 6, 8, 10.
35. In AC windings, the number of slots per pole per phase q=q=Z/2p/m (assuming the number of slots is Z, the number of pole pairs is p, and the number of phases is m). .In AC windings, there are both 120o phase bands and 60o phase bands. Among them, the fundamental winding coefficient and back electromotive force of the 60o phase band are higher.
36. The symmetrical component method can be used to analyze the asymmetric operation of transformers and synchronous motors. The premise of its application is that the system is linear. Therefore, the principle of superposition can be applied to decompose the asymmetric three-phase power system into positive sequence, negative sequence, Three symmetrical three-phase systems such as zero sequence.
37. The calculation formula of the short-distance coefficient is ky1= sin(p/2×y1/t), and its physical meaning is that the short-distance causes the discount (or reduction) of the back-EMF (or magnetomotive force) compared with the whole-distance Coefficient). The calculation formula of the distribution coefficient is kq1= sin(qa1/2) /q/ sin(a1/ 2), and its physical meaning is that when q coils are sequentially different by a1 electrical angle, the back EMF (or magnetomotive force) is relatively concentrated The coefficient (or discount) reduced by the situation.
38. The current transformer is used to measure current, and its secondary side cannot be open. The voltage transformer is used to measure voltage, and its secondary side cannot be short-circuited.
39. A motor is a device that converts mechanical energy into electrical energy (or vice versa), or changes an AC voltage level to another AC voltage level. From the perspective of energy conversion, motors can be divided into three categories: transformers, motors, and generators.
40. The calculation formula of the slot pitch electric angle a1 is a1=p×360o/Z. It can be seen that the slot pitch electrical angle a1 is equal to p times the slot pitch mechanical angle am.
41. The principle of transformer winding reduction is to ensure that the magnetomotive force of the winding remains unchanged before and after the reduction, and that the active and reactive power of the winding remain unchanged.
42. The characteristic of the efficiency characteristic curve of the transformer is that there is a maximum value, that is, the maximum value is reached when the variable loss is equal to the constant loss.
43. The no-load test of the transformer is usually applied and measured on the low-voltage side. In the short-circuit test of the transformer, voltage is usually applied and measured on the high-voltage side.
44. When transformers are operated in parallel, the conditions for no-load and no circulating current are: the same transformation ratio and the same connection group number.
45. When transformers are operated in parallel, the principle of load distribution is: the unit value of the load current of the transformer is inversely proportional to the unit value of the short-circuit impedance. The condition that the capacity of the transformer can be fully utilized in parallel operation is: the unit value of the short-circuit impedance must be equal, and their impedance angles must also be equal.
1.27mm (0.050") Pitch Female Headers
Like the 1.27mm pitch male header, the 1.27mm pitch female header is used in densely-packed devices, requiring space-saving connections. The low profile, 1.27mm pitch female header addresses the need for connecting a variety of board-to-board configurations, with vacuum pick and place that makes it suitable for high volume automated manufacturing. It can be available in varying elevated stack heights, pass-through, rugged, high-density, and in numerous low-cost designs.
Antenk offers 1.27mm pitch female headers in either SMT or THM orientation at high quality and affordable China-quoted price that snuggly fits with the pins of a male header and acts as a receptacle.
Assembly and service is simple with either vertical (straight), elevated or at a right angle orientation, which can dissipate current of about 1.0 A or less in a tape and reel packaging. The filleted corners can also remove shadowing allowing optimization of LED output.
The 1.27mm pitch female headers are commonly found in PC`s and are also made to work in Arduino boards, Arduino Pro and Arduino Mega with either single or double-row female headers, facilitating connections for programming and incorporation into other circuits. They have the perfect height for clearing the USB-B connector and great for stacking multiple shields.
Female header always called as [Header connector", Antenk provide widely range of header connector, from 2.54mm (.100″ inch) pitch to 1.0mm (.039″ inch) pitch. The number of pins (contacts) is from 2 to 40 pins per orw. There are three type: Straight (Dip Vertical), Right angle, SMT (surface mount).
If you can not find the items you interest from above items, welcome to contact us, and you will always get fully responsive from us.
Applications of 1.27mm Pitch Female Headers
Its small size is most suitable for PCB connections of small equipment and devices such as:
Arduino Boards
Architectural and sign lighting
Retail and display lighting
Fluorescent LED retrofit lighting
Cabinet or furniture lighting
Commercial / residential cove lighting
WiFi equipment
Gaming consoles,
Measurement instruments
Medical Diagnostic and Monitoring equipment
Communications: Telecoms and Datacoms
Industrial and Automotive Control and Test
At one side of this female header is a series of pins which can either be mounted and soldered directly onto the surface of the PCB (SMT) or placed into drilled holes on the PCB (THM).
Through-Hole (Poke-In)
Best used for high-reliability products that require stronger connections between layers.
Aerospace and military products are most likely to require this type of mounting as these products experience extreme accelerations, collisions, or high temperatures.
Useful in test and prototyping applications that sometimes require manual adjustments and replacements.
1.27mm vertical single row female header, 1.27mm vertical dual row female header, 1.27mm Elevated single row female header, 1.27mm Elevated dual row female Header, 1.27mm right-angle single row female header and 1.27mm right-angle dual row female header are some examples of Antenk products with through-hole mount type.
Surface-Mount
The most common electronic hardware requirements are SMT.
Essential in PCB design and manufacturing, having improved the quality and performance of PCBs overall.
Cost of processing and handling is reduced.
SMT components can be mounted on both side of the board.
Ability to fit a high number of small components on a PCB has allowed for much denser, higher performing, and smaller PCBs.
1.27mm Right-angle Dual Row female header, 1.27mm SMT Single row female header, 1.27mm SMT Dual row female header and 1.27mm Elevated Dual Row female Header are Antenk`s SMT female headers.
Soldering Temperature for 1.27mm Pitch Female Headers
Soldering SMT female connectors can be done at a maximum peak temperature of 260°C for maximum 60 seconds.
Pin-Type: Vertical (Straight) and Right-Angle
1.27mm pitch female headers may be further classified into pin orientation as well, such as vertical or straight female header or right-angle male header.
Vertical or Straight Female Header Orientation
One side of the series of pins is connected to PCB board in which the pins can be at a right-angle to the PCB surface (usually called "straight" or [vertical") or.
Right-Angle Pin Female Header Orientation
Parallel to the board's surface (referred to as "right-angle" pins).
Each of these pin-types have different applications that fit with their specific configuration.
PCB Connector Stacking
Profile Above PCB
This type of configuration is the most common way of connecting board-to-board by a connector. First, the stacking height is calculated from one board to another and measured from the printed circuit board face to its highest insulator point above the PCB.
Elevated Sockets/Female Headers
Elevated Sockets aka Stacked sockets/receptacles or Mezzanine are simply stacked female headers providing an exact distance requirement between PCBs that optimizes electrical reliability and performance between PCB boards.
Choosing this type of stacking configuration promotes the following benefits:
Connector Isolation - the contacts are shrouded preventing cable connection mishaps and good guidance for the mating header connectors.
For off-the-shelf wireless PCB module, stacking height is optimized with elevated sockets.
Offers superior strength and rigidity.
Polarisation prevents users from inverted insertion.
Single, Dual or Multiple Number of Rows
For a 1.27mm straight or vertical female header, the standard number of rows that Antenk offers ranges from 1 to 2 rows. However, customization can be available if 3 ,4 or n number of rows is needed by the customer. Also, the number of contacts for the single row is about 2-40 pins while for dual row, the number contacts may vary from 2-80 pins.
Pin Material
The pins of the connector attached to the board have been designed with copper alloy. With customer`s demand the pins can be made gold plated.
Custom 1.27mm Pitch Female Headers
Customizable 1.27 mm pitch female headers are also available, making your manufacturing process way faster as the pins are already inserted in the headers, insulator height is made at the right size and the accurate pin length you require is followed.
Parts are made using semi-automated manufacturing processes that ensure both precision and delicacy in handling the headers before packaging on tape and reel.
Tape and Reel Packaging for SMT Components
Antenk's SMT headers are offered with customizable mating pin lengths, in which each series has multiple number of of circuits, summing up to a thousand individual part number combinations per connector series.
The tape and reel carrier strip ensures that the headers are packaged within accurately sized cavities for its height, width and depth, securing the headers from the environment and maintaining consistent position during transportation.
Antenk also offer a range of custom Tape and reel carrier strip packaging cavities.
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ShenZhen Antenk Electronics Co,Ltd , https://www.atkconnectors.com